Hi jenkins, first let me welcome you to healing well forum, we are happy to have you. I just have to commend your client for working towards losing the weight. It isnt easy I know...my mother was overweight and had really bad knees (DJD) so she ended up having gastric bypass done then total knee replacements. It is so difficult to exercise when you have multiple health problems such as that.
I too would also say that her shortness of breath would be from her weight. It puts so much stress on the heart and lungs. With you being a personal trainer I am sure you are well versed on this.